In the manufacture of electronic devices such as integrated circuits, a target substrate, such as a semiconductor wafer, is subjected to various processes, such as film formation, etching, oxidation, diffusion, reformation, annealing, and natural oxide film removal. Silicon-containing films are an important part of many of these processes.
Silicon-containing films are used for a wide variety of applications in the semiconductor industry. Examples of silicon-containing films include epitaxial silicon, polycrystalline silicon (poly-Si), and amorphous silicon, epitaxial silicon germanium (SiGe), silicon germanium carbide (SiGeC), silicon carbide (SiC), silicon nitride (SiN), silicon carbonitride (SiCN), and silicon carboxide (SiCO). As circuit geometries shrink to smaller feature sizes, lower deposition temperatures for Si-containing films are preferred, for example, to reduce thermal budgets.
Silicon nitride films have very good oxidation resistance and insulating qualities. Accordingly, these films have been used in many applications, including oxide/nitride/oxide stacks, etch stops, oxygen diffusion barriers, and gate insulation layers, among others. Several methods are known for forming a silicon nitride film on the surface of a semiconductor wafer by Chemical Vapor Deposition (CVD). In thermal CVD, a silane gas, such as monosilane (SiH4) or polysilanes, is used as a silicon source gas.
SiN film formation has also been carried out via atomic layer deposition using halosilane and ammonia. However, this process requires high temperatures, in excess of 500° C., to effect clean conversion and eliminate NH4X byproducts. In device manufacturing, processes that can be performed at lower temperatures are generally desired for thermal budget and other reasons.